Chemical Engineering Journal 170 (2011) 395–410 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Review Carbon nanotubes as adsorbents in environmental pollution management: A review Xuemei Ren a , Changlun Chen a,b , Masaaki Nagatsu b , Xiangke Wang a,∗ a Key Lab of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei 230031, PR China b Graduate School of Science and Technology, Shizuoka University, 3-5-1, Johoku, Naka-ku, Hamamatsu 432-8561, Japan article info Article history: Received 22 April 2010 Received in revised form 12 July 2010 Accepted 17 August 2010 Keywords: Carbon nanotubes Adsorption Organic pollutants Inorganic pollutants abstract Carbon nanotubes (CNTs) have aroused widespread attention as a new type of adsorbents due to their outstanding ability for the removal of various inorganic and organic pollutants, and radionuclides from large volumes of wastewater. This review summarizes the properties of CNTs and their properties related to the adsorption of various organic and inorganic pollutants from large volumes of aqueous solutions. Their application as adsorbents for the preconcentration and immobilization of all kinds of pollutants from gas streams and large volumes of aqueous solutions are summarized, and the further research trend on CNTs in the removal of pollutants is also given. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Carbon nanotubes (CNTs), a new member of the carbon family, were first discovered by Iijima in 1991 [1]. Since then, CNTs have been the focus of considerable research because of their unique physicochemical properties. The first observed CNTs were mul- tiwalled carbon nanotubes (MWCNTs) (see Fig. 1a), consisting of up to several tens of graphitic shells with adjacent shell separa- tion of ∼0.34 nm, diameters of ∼1 nm and large length/diameter ratio [2]. MWCNTs can be considered as elongated fullerene [3]. A few months after Iijima’s discovery, Ebbesen and Ajayan [4] published their work on the bulk synthesis of MWCNTs by arc- ing graphite electrodes in inert atmospheres at optimum current and pressure conditions. However, it is necessary to note that the first images of CNTs were obtained by Oberlin et al. by pyroly- sis of benzene and ferrocene at 1000 ◦ C in the mid-1970s [5]. In 1993, smaller-diameter, single walled carbon nanotubes (SWCNTs) (see Fig. 1b) were independently discovered by Iijima and Ichi- hashi [6] and Bethune et al. [7] using arc-discharge method and metal (iron and cobalt) as catalysts. CNTs have been termed ‘mate- rials of the 21st century’ [8] due to their unique properties such as functional mechanical, thermal, electrical and optoelectronic prop- erties which depend on atomic arrangement (how the sheets of graphite are ‘rolled’), the diameter and length of the tubes, and the morphology, or nanostructure [9,10]. At present, theoretical ∗ Corresponding author. Tel.: +86 551 5592788; fax: +86 551 5591310. E-mail address: xkwang@ipp.ac.cn (X. Wang). and experimental investigations on CNTs on their properties and application in multidisciplinary areas increase exponentially. Because of the current and increasing investment and the poten- tial widespread use, CNTs are spread quickly in the environment. Several studies suggest that they are toxic to human beings and other organisms, and their presence in the environment affects the physicochemical behavior of common environmental pollutants, such as heavy metal ions as reviewed by Rao et al. [12] and organic compounds as reviewed by Pan and Xing [13]. Because of their sur- face functional groups and hydrophobic surfaces, CNTs show strong interactions with both heavy metal ions and organic compounds. To determine overall environmental and health impact of CNTs once escaped into the environment, the effects of CNTs on com- mon environmental contaminants including organic and inorganic pollutants need to be evaluated. This paper reviews the current state of the application of CNTs including MWCNTs and SWCNTs in the removal of organic and inor- ganic pollutants from gas and large volumes of aqueous solutions. This review is not intended to be comprehensive, as our focus is on exploiting the exceptional adsorption properties of CNTs towards the development of novel adsorption materials. 2. Adsorption properties of CNTs The adsorption-related applications of CNTs to solve environ- mental pollution problems have received considerable attention in recent years. CNTs are relatively new adsorbents and hold inter- esting positions in carbon-based adsorptive materials for many reasons. On one hand, they provide chemically inert surfaces for 1385-8947/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2010.08.045